Connecting the DoTs: A Summoner Guide

[Kona_Nightwind]

I need a little help. Been stuck on AS3 for awhile and Id like to do a few things better if I can.
1. First off I've been using Sleighs opener, and I've seem to run into a problem. My fester during DWT just misses my pot half the time. Is this me just being bad at activating my skills. My spell speed has dropped quite a bit, so maybe I got lazy on activation.
2. I use Garuda the entire fight, contagion just lines up perfectly with everything. Then of course add phase. Is there anytime to use ifrit that's beneficial?
3. During adds I don't use any cds. I miasma everything I can, miasma 2 if a few are close, bio when I can, and just leave garuda on what ever mob gets the least attention. In the next phase we save cds until after polarities than pop everything. Is there a better way to do this? MNK,DRG,MCH,SMN is dps comp. PHD,WAR,WHM,SCH is the other.
4. Was told I'm consistently top dps until add phase, was thinking about switching to BLM for this fight. But would need to gear it up a little. Is it worth it? And is it worth it for AS4?
Sorry if these things have come up. I just don't have the time I used to to research and play.